During the first study visit, subjects will receive a physical exam and an electroencephalogram (EEG), which measures brain activity. Research staff will put a cap on your head that has sensors which measure your brain activity. There is no risk of electrical shock. In addition to the sensors in the cap, two clips will be put on your ears. EEG activity will be collected for 20 minutes: you will have your eyes open for ten minutes, and then have your eyes closed for ten minutes.